1. Field of the Invention
The present invention relates to the use of an aqueous composition, free of organic solvents, plasticizers and additional tackifiers, containing water and 20-99% by weight of a polymer having a glass transition temperature below xe2x88x9225xc2x0 C. and 1-80% by weight of a filler, the percentages by weight being based on the sum of the components of the aqueous composition, with the exception of water, as a floor adhesive.
2. Discussion of the Background
EP-A-490 191 discloses solvent-free floor adhesives based on an acrylate dispersion. The floor adhesives described there inevitably contain a tackifier and a plasticizer.
DE-A-41 41 168 relates to contact adhesive dispersions of vinyl ester/acrylate copolymers. The copolymers have a glass transition temperature of from xe2x88x9220 to +20xc2x0 C.
In principle, it is desirable for adhesives to have very few components, in order to facilitate their preparation and reduce costs. In particular, adhesives should be free of components which escape from the adhesive bond during subsequent use and can lead to undesirable emissions.)
In the case of the performance characteristics, good tack (for example good wet and dry grab), and good heat distortion resistance of the adhesive bond are particularly desirable.
It is an object of the present invention to provide adhesives, in particular floor adhesives, having the abovementioned properties.
The aqueous compositions contain preferably from 30 to 70, particularly preferably from 40 to 60, % by weight of a polymer having a glass transition temperature below xe2x88x9225xc2x00 C. and from 30 to 70, particularly preferably from 40 to 60, % by weight of a filler.
The percentages by weight are based on the sum of the components of the aqueous composition, with the exception of water, ie. essentially on the solids content of the composition.
The polymer is preferably a polymer obtained by free radical polymerization of ethylenically unsaturated monomers.
The polymer may be composed of, for example, C1-C20-alkyl (meth)acrylates, vinyl esters of carboxylic acids of up to 20 carbon atoms, vinylaromatics of up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, nonaromatic hydrocarbons having at least 2 conjugated double bonds or mixtures of these monomers.
The abovementioned monomers may be present in the polymer, for example, in amounts of from 60 to 100, preferably from 80 to 100, particularly preferably from 90 to 99.8, % by weight, based on polymer.
Examples are alkyl (meth)acrylates having a C1-C10-alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.
Mixtures of alkyl (meth)acrylates are also particularly suitable.
Vinyl esters of carboxylic acids of 1 to 20 carbon atoms are, for example, vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and vinyl acetate.
Suitable vinylaromatic compounds are vinyltoluene, xcex1- and p-methylstyrene, xcex1-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Examples of nitriles are acrylonitrile and methacrylonitrile.
The vinyl halides are ethylenically unsaturated compounds substituted by chlorine, fluorine or bromine, preferably vinyl chloride and vinylidene chloride.
Examples of nonaromatic hydrocarbons having 2 to 8 carbon atoms and at least two olefinic double bonds are butadiene, isoprene and chloroprene.
(Meth)acrylates and mixtures thereof are particularly preferred.
Further monomers, which may be present in the polymer in amounts of, for example, from 0 to 40, preferably from 0 to 20, particularly preferably from 0.2 to 10, % by weight, are in particular C1-C10-hydroxyalkyl (meth)acrylates, (meth)acrylamide and the derivatives thereof substituted on the nitrogen by C1-C4-alkyl, ethylenically unsaturated carboxylic acids, dicarboxylic acids, half-esters and anhydrides thereof, for example (meth)acrylic acid, maleic acid, fumaric acid, maleic anhydride, maleic and fumaric half-esters and itaconic acid. A content of from 0.2 to 5% by weight of an ethylenically unsaturated carboxylic acid is very particularly preferred.
The glass transition temperature of the polymer is below xe2x88x9225xc2x0 C., in particular from xe2x88x9225 to xe2x88x9260xc2x0 C., particularly preferably from xe2x88x9230 to xe2x88x9250xc2x0 C.
The glass transition temperature of the polymer can be determined by conventional methods, such as differential thermal analysis or differential scanning calorimetry (cf. for example ASTM 3418/82, ie. midpoint temperature).
The number average molecular weight Mn of the polymer is preferably greater than 10,000, in particular greater than 20,000, particularly preferably greater than 30,000, and the weight average molecular weight Mw is preferably greater than 250,000 (determined by gel permeation chromatography using polystyrene as standard in a polymer solution in tetrahydrofuran after sedimentation of the insoluble components); the proportion of the insoluble components in the polymer is preferably from 0-90, particularly preferably 20-70, very particularly preferably from 40 to 60, % by weight, based on the polymer.
The polymer is prepared by free radical polymerization. Suitable polymerization methods, such as mass, solution, suspension or emulsion polymerization, are known to a person skilled in the art.
The copolymer is preferably prepared by solution polymerization with subsequent dispersing in water or particularly preferably by emulsion polymerization, so that aqueous copolymer dispersions are formed.
The emulsion polymerization can be carried out batchwise, with or without the use of seed latices, initially taking all or individual components of the reaction mixture, or preferably initially taking part of the components and subsequently metering in the components or individual components of the reaction mixture, or by the metering method without initially taking any components.
In the emulsion polymerization, the monomers can be polymerized in a conventional manner in the presence of a water-soluble initiator and of an emulsifier at, preferably, from 30 to 95xc2x0 C.
Examples of suitable initiators are sodium persulfate, potassium persulfate, ammonium persulfate, tert-butyl hydroperoxides, water-soluble azo compounds or redox initiators, such as H2O2/ascorbic acid.
The emulsifiers used are, for example, alkali metal salts of relatively long-chain fatty acids, alkylsulfates, alkylsulfonates, alkylated arylsulfonates or alkylated diphenyl ether sulfonates. Other suitable emulsifiers are reaction products of alkylene oxides, in particular ethylene oxide or propylene oxide, with fatty alcohols, fatty acids or phenol, or alkylphenols.
In the case of aqueous secondary dispersions, the copolymer is first prepared by solution polymerization in an organic solvent and then dispersed in water with the addition of salt formers, for example of ammonia to carboxyl-containing copolymers, without the use of an emulsifier or dispersant. The organic solvent can be distilled off. The preparation of aqueous secondary dispersions is known to a person skilled in the art and is described in, for example, DE-A-37 20 860.
Regulators may be used in the polymerization in order to regulate the molecular weight. For example, xe2x80x94SH-containing compounds, such as mercaptoethanol, mercaptopropanol, thiophenol, thioglycerol, ethyl thioglycolate, methyl thioglycolate and tert-dodecyl mercaptan, are suitable.
The solids content of the polymer dispersions obtained is preferably from 40 to 80, particularly preferably from 45 to 75, % by weight. High polymer solids contents can be obtained, for example, by processes which are described in German Patent Application P 4 307 683.1 or European Patent 37 923.
The aqueous composition also contains at least one filler in addition to the polymers. Suitable fillers are, for example, finely milled or precipitated chalks having a mean particle diameter of, in general, from 2 to 50 xcexcm and/or quartz powder having a conventional mean particle diameter of from 3 to 50 xcexcm.
The composition may furthermore contain wetting agents or dispersants, for example for the fillers thickeners and, for example, further conventional additives, such as antifoams and preservatives.
The aqueous composition may contain, for example, from 0 to 5% by weight of wetting agents or dispersants, from 0 to 10% by weight of thickeners, from 0 to 1% by weight of preservatives and from 0 to 5% by weight of antifoams. The stated weights are based on the sum of all components of the aqueous composition, with the exception of water.
The composition is free of organic solvents and plasticizers, such as butyl acetate, toluene or phthalates. It therefore contains essentially no organic compounds having a boiling point below 260xc2x0 C. at atmospheric pressure (1 bar).
The composition is also free of tackifiers,such as rosins, which are usually additionally employed.
The aqueous composition can be prepared in a simple manner by adding the fillers and, if required, further additives to the aqueous polymer dispersion obtained in the emulsion polymerization, while stirring.
The water content of the prepared composition is in general from 7 to 50, in particular from 10 to 30, % by weight, based on the total aqueous composition.
The aqueous composition is suitable as floor adhesive for floor coverings, for example comprising PVC, in the form of multilayer coverings or homogeneous coverings, foam coverings having a textile backing, for example jute, polyester nonwoven, rubber coverings, textile coverings having different backings, such as polyurethane foam, styrene/butadiene foam, textile secondary backings, needle felt floor coverings, polyolefin coverings or linoleum coverings, on surfaces such as wood, stone, concrete, ceramic tiles, metal surfaces or the like.
The adhesive can be applied to the substrate, for example, by means of a toothed strip. After drying in the air in the usual manner, the floor covering is laid. In terms of the procedure, the novel adhesive is equivalent to the solvent-containing synthetic resin adhesives and the traditional one-sided dispersion adhesives. With regard to the processability, the new adhesive is similar to solvent-containing adhesives. The novel adhesive composition has a good level of performance characteristics, such as peel strength, shear strength, wet grab and dry grab and high heat distortion resistance.
In the examples which follow, parts and percentages are by weight, unless stated otherwise.